Author Topic: Carb on the KX?  (Read 6648 times)

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kawdude

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Carb on the KX?
« on: January 10, 2004, 05:14:18 PM »
Just for piece of mind...

Isn't a 39mm standard for the big KX.  Someone telling me should be a 38 and not a 39mm

Offline demographic

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Re: Carb on the KX?
« Reply #1 on: January 11, 2004, 12:57:55 AM »
Quote from: kawdude
Just for piece of mind...

Isn't a 39mm standard for the big KX.  Someone telling me should be a 38 and not a 39mm


Kehin PWK 39 is standard on mine and I think on all the later ones.
Although I have heard that PWK 39s are really 39.5 mil anyway, could be wrong about that though :? Not gonna lose sleep over it either :D

Offline Paul

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Carb on the KX?
« Reply #2 on: January 11, 2004, 02:35:36 AM »
39.5 PWK is correct :wink:

Offline doordie

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Carb on the KX?
« Reply #3 on: January 11, 2004, 11:15:32 AM »
I wonder if it?s the best carburator size (39,5mm)for a 500cc when you use it at MX-tracks?
Look at mossbargers site www.mossbargerracing.com,they says 36-38mm would be best for the higher velocity(airspeed) it produce with smaller carburator.Maybe someone will try a smaller carb.. size?
Iceroad champion 2006,still 2007,even 2008 without a single race!

kawdude

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Carb on the KX?
« Reply #4 on: January 11, 2004, 11:46:05 AM »
I'm no expert but I would think that a 36 would be too small although it could be made to work.  I was under the impression that this size of engine was not so concerned with velocity but volume.  Granted I understand the benefit for higher velocity but at mid range and above the smaller carbs would allow enough air to pass.  Interesting topic!

mikesmith

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Carb on the KX?
« Reply #5 on: January 11, 2004, 12:38:25 PM »
I read Destry Abbott runs a KX250 carb bored out to 38.5,and he's racing desert.

kawdude

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Carb on the KX?
« Reply #6 on: January 11, 2004, 01:57:32 PM »
Doesn't the 250 carb have the pump on it?

Offline doordie

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Carb on the KX?
« Reply #7 on: January 12, 2004, 01:34:47 AM »
The reedcage and the area of the reeds decide how much air going through to the intake.If a reedcage have less area/flow than the carburatorsize, it should be only airspeed who can press more air into engine.So, too big carburator produce less airspeed,less hp. :(
The problem is to determind what size is too big! :wink:

Just my thoughts  :)
Iceroad champion 2006,still 2007,even 2008 without a single race!

mikesmith

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Carb on the KX?
« Reply #8 on: January 12, 2004, 10:21:48 AM »
You mean the power jet?You have to have electrical power to run it (I think at one time on the 125 Kawasaki had the power jet carb on the bike,but the power jet wasnt even wired up) and Destry's bike didnt have a lighting coil,so even if it was a power jet carb it wasnt wired up.You think as long as the 500 has been around there'd be more info on pipes and carbs or differnt combos ect.

kawdude

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Carb on the KX?
« Reply #9 on: January 12, 2004, 12:49:07 PM »
What is the stock slide and needle that is used on the 500?

mikesmith

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Carb on the KX?
« Reply #10 on: January 12, 2004, 07:13:22 PM »
Slide is a 7.0,needle's N82R.I'm sure Rick cut some of his slide to lean it out a little and it worked well for him.Any one else try this or a differnt slide than stock?

Twist-a-grip

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Carb on the KX?
« Reply #11 on: January 13, 2004, 12:12:01 PM »
There is a trade off on sizes I think.  If I remember right my '86 had a 40mm mikuni.  '91 has a 39 kehien.  Factory must have been looking for better low end or the latter is more efficient.  The smaller the carb the better velocity/low end throttle response.  The bigger the better top end breathing capability.  You gain in one area and lose in another unless modifications to the engine create a different demand.

Offline John

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Carb on the KX?
« Reply #12 on: January 13, 2004, 10:39:04 PM »
Where does the moose spacer effect fit in to all of this? Increasing the distance between the carb and cylinder give you a similar effect.

//John

Offline YUNGGUNNAZ

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spacer
« Reply #13 on: January 14, 2004, 01:13:51 PM »
John,spacer does help the bottom to midrange.tie this in with a polish rod beams to ward off some deflection of incoming charge with smooth crankcase and you should feel the size 14 to the rearend effect.now this was two cents worth.also play with spacer width.